Who says that the most knowledgable people are adults?
The spy starring in Sabotage, part 2. He may be a double-edged character.
Fullick is one of three leaders of the Black Hand Rogues Guild. He has been posing as a noble since he joined the guild and it has gone to his head. He acts the part at all times much to the amusement of other guildmembers. Nobody would mock him to his face though since he is a master swordsman trained by the best nobility could afford.
On a location with numerous webs, and at least one big spider, there is a something inside a cocoon. It is humanoid in shape, still moving. If the heroes free it (not before they kill or drive away the spiders), they meet a ... zombie!
The poor zombie wandered the dungeon alone, and tried to kill a big living creature (= a spider). The spider used the usual treatment, even if this victim did not look tasty. The zombie can be easily killed as any other zombie. It got but several doses of spider-poison, so can be something worth if it is extracted. You can mention to a druid or ranger the fact the spider had no poison anymore.